Multilayer inductor

ABSTRACT

A multilayer inductor is disclosed. The multilayer inductor includes a bottom magnetic layer having an external conductive pattern formed on a bottom surface thereof for connection to a substrate such as a printed circuit board. The bottom external conductive pattern includes signal/power contacts and first and second inductor electrodes. A top magnetic layer includes a top external conductive pattern having signal/power contacts and inductor electrode contacts. An inductor conductive pattern formed on the top surfaces of intermediate magnetic layers disposed between the top and bottom magnetic layers are electrically coupled to each other by means of through holes to form a spiral inductor element. The spiral inductor element is coupled to the first inductor electrode by means of a through hole formed in the bottom magnetic layer and to the second inductor electrode by means of power conductive traces formed on side surfaces of the multilayer inductor. Flux density reducing layers may be inserted directly above the bottom magnetic layer and directly below the top magnetic layer. Signal/power conductive traces formed on side surfaces of the multilayer inductor provide signal/power routing between the top magnetic layer signal/power contacts and the bottom magnetic layer signal/power contacts. The top external conductive pattern accommodates a semiconductor chip in a flip chip configuration.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to multilayer inductors and moreparticularly to a multilayer inductor adapted to accommodate a flip chipon a top surface thereof and having conductive patterns formed on itstop, bottom and side surfaces.

2. Description of Related Art

Multilayer inductors are well known in the art. For example a chip-typeinductor comprising a laminated structure is disclosed in U.S. Pat. No.4,543,553. The structure includes a plurality of magnetic layers inwhich linear conductive patterns extending between the respectivemagnetic layers are connected successively in a form similar to a coilso as to produce an inductance component. The conductive patterns formedon the upper surfaces of the magnetic layers and the conductive patternsformed on the lower surfaces of the magnetic layers are connected witheach other in the interfaces of the magnetic layers and are alsoconnected to each other via through-holes formed in the magnetic layersso that the conductive patterns are continuously connected in a formsimilar to a coil.

U.S. Pat. No. 5,032,815 discloses a lamination type inductor having aplurality of ferrite sheets assembled one above the other and laminatedtogether, the uppermost and lowermost sheets being end sheets havinglead-out conductor patterns thereon and conductor patterns on thesurfaces of the end sheets which face each other which are connected tothe lead-out conductor patterns and which are for connection toconductor patterns on intermediate sheets, and a plurality ofintermediate ferrite sheets, each having a conductor pattern on onesurface thereof which corresponds to a 0.25 turn of an inductor coil anda conductor pattern on the other surface which corresponds to a 0.5 turnof an inductor coil, each ferrite sheet having an opening therethroughthrough which the conductor patterns of the 0.25 and 0.5 turn areelectrically connected to form a 0.75 turn of an inductor coil on eachferrite sheet. The conductor patterns on the successive intermediatesheets are connected to each other for forming an inductor coil having anumber of turns which is a multiple of 0.75 and the conductor patternson the upper surface of the uppermost of the plurality of intermediateferrite sheets and the lower surface of the lowermost of theintermediate ferrite sheets are electrically connected to the conductorpatterns on the surfaces of the end sheets which face each other forforming with the last-mentioned conductor pattern a complete inductorcoil.

U.S. Pat. No. 6,630,881 discloses a method for producing a multi-layeredchip inductor that includes the steps of: forming coil-shaped internalconductors inside a green ceramic laminate, each of which coil-shapedinternal conductors is spiraled around an axial line in the laminatingdirection of the green ceramic laminate; applying an external electrodepaste onto at least one laminating-direction surface of the greenceramic laminate, which external electrode paste connects to an end ofthe coil-shaped internal conductor; cutting the green ceramic laminatealong the laminating direction into chip-shaped-green ceramic laminateseach having the coil-shaped internal conductor inside; and firing eachof the chip-shaped green ceramic laminates and baking the externalelectrode paste to form an external electrode.

Another laminated inductor is disclosed in U.S. Pat. No. 7,046,114.Thelaminated inductor includes ceramic sheets provided with spiral coilconductor patterns of one turn, ceramic sheets provided with spiral coilconductor patterns of two turns, and ceramic sheets provided withlead-out conductor patterns, which are laminated together. The coilconductor patterns are successively electrically connected in series inregular order through via holes. The via holes are disposed at fixedlocations in the ceramic sheets.

U.S. Pat. No. 6,930,584 discloses a microminiature power converterincluding a semiconductor substrate on which is formed a semiconductorintegrated circuit, a thin film magnetic induction element, and acapacitor. The thin film magnetic induction element includes a magneticinsulating substrate, and a solenoid coil conductor in which a firstconductor is formed on a first principal plane of the magneticinsulating substrate, a second conductor is formed on a second principalplane of the magnetic insulating substrate, and a connection conductoris formed in a through hole passing through the entire magneticinsulating substrate. The disclosed power converter suffers thedisadvantage that plating the deep through hole is difficult andexpensive.

U.S. Published Patent Application No. 2006/0227518 discloses a thin filmmagnetic induction element including a ferrite substrate, a coilprovided across the ferrite substrate and including connectionconductors and coil conductors, and terminals provided on perimeterportions of the substrate. Terminals capable of being adversely affectedby an induced magnetic flux, such as a VDD terminal, a CGND terminal, anIN terminal, a PVDD terminal, a PGND terminal, an FB terminal, a CEterminal, and an AL terminal are arranged along the Y-direction of thesubstrate, in which the magnetic flux density is low. Terminalssubstantially incapable of being adversely affected by an inducedmagnetic flux are arranged along the X-direction of the substrate, inwhich the magnetic flux density is high. A micro electric powerconverter having the thin film magnetic induction element is lesssusceptible to circuit malfunction.

Although it is possible to surface mount a flip chip on top of theinductors disclosed by the above U.S. Pat. No. 6,930,584 and U.S.Published Patent Application No. 2006/0227518,the deposition ofconductive layers, for example Cu/Ni layers on top, bottom and sidewalls of the inductor requires special thick metal deposition technologywhich is difficult and costly and makes the final product lesscompetitive. Furthermore, the disclosed inductors are single layerinductors, not multilayer inductors.

In view of the foregoing, there is a need for a cost-effectivemultilayer inductor adapted to accommodate a flip chip on a top surfacethereof and having conductive patterns formed on its top, bottom andside surfaces. Further objects and advantages of the present inventionwill be apparent from the following detailed description of theinvention and associated drawings.

SUMMARY OF THE INVENTION

The multilayer inductor of the invention overcomes the disadvantages ofthe prior art and achieves the objectives of the invention by providinga multilayer inductor comprising a plurality of magnetic layerslaminated together. In a first embodiment, a bottom magnetic layerincludes an external conductive pattern formed on a bottom surfacethereof for connection to a substrate such as a printed circuit board.The bottom external conductive pattern includes signal/power contactsand first and second inductor electrodes. A top magnetic layer includesan external conductive pattern having signal/power contacts, and aninductor electrode contact. An inductor conductive pattern formed on thetop surface of the bottom magnetic layer and inductor conductivepatterns formed on the top surfaces of intermediate magnetic layersdisposed between the top and bottom magnetic layers are electricallycoupled to each other by means of through holes to form a spiralinductor element. The spiral inductor element is coupled to the firstinductor electrode by means of a through hole formed in the bottommagnetic layer and to the second inductor electrode by means of powerconductive traces formed on side surfaces of the multilayer inductor.Signal/power conductive traces formed on side surfaces of the multilayerinductor provide signal/power routing between the top magnetic layersignal/power contacts and respective bottom magnetic layer signal/powercontacts. The top external conductive pattern accommodates asemiconductor chip in a flip chip configuration.

In accordance with a second embodiment of the multilayer inductor, abottom magnetic layer includes an external conductive pattern formed ona bottom surface thereof. The bottom external conductive patternincludes signal/power contacts and first and second inductor electrodes.A top external conductive pattern includes signal/power contacts and aninductor electrode contact. Inductor conductive patterns formed on thetop surfaces of intermediate magnetic layers disposed between the topand bottom magnetic layers are electrically coupled to each other bymeans of through holes to form a spiral inductor element. The spiralinductor element is coupled to the first inductor electrode by means ofa through hole formed in the bottom magnetic layer and a through holeformed at a first end of the inductor conductive pattern of theintermediate magnetic layer overlaying the bottom magnetic layer. Thespiral inductor element is coupled to the second inductor electrode bymeans of conductive power traces formed on side surfaces of themultilayer inductor. Signal/power conductive traces formed on sidesurfaces of the multilayer inductor provide signal/power routing betweenthe top magnetic layer signal/power contacts and respective bottommagnetic layer signal/power contacts. The top external conductivepattern accommodates a semiconductor chip in a flip chip configuration.

In accordance with an aspect of the claimed invention, a multilayerinductor comprises a bottom magnetic layer including an externalconductive pattern formed on a bottom surface thereof, the externalconductive pattern including a plurality of signal/power contactsdisposed at edges thereof and first and second inductor electrodes; atop magnetic layer including an external conductive pattern formed on atop surface thereof, the external conductive pattern including aplurality of signal/power contacts disposed at edges thereof and aninductor electrode contact; and a plurality of intermediate magneticlayers stacked between the bottom magnetic layer and the top magneticlayer, each intermediate magnetic layer including a plurality ofsignal/power contacts disposed at edges thereof and an inductorconductive pattern, each of the plurality of intermediate magnetic layersignal/power contacts electrically coupled to respective top and bottommagnetic layer signal/power contacts to form external signal/powerroutes between the top magnetic layer external conductive pattern andthe bottom magnetic layer external conductive pattern, each of theintermediate magnetic layer inductor conductive patterns coupled to eachother to form a spiral inductor element, the spiral inductor elementcoupled at a first end thereof to the top magnetic layer inductorelectrode contact and at a second end thereof to the first inductorelectrode, the top magnetic layer inductor electrode contact coupled tothe second inductor electrode by an external inductor power route,comprising at least one of the external signal/power routes.

In accordance with another aspect of the claimed invention, method ofmanufacturing a multilayer inductor comprises the steps of formingexternal and internal vias in a plurality of magnetic green sheets;printing and curing conductive patterns on the plurality of magneticgreen sheets; stacking and pressing the plurality of magnetic greensheets together to form an internal inductor element and externalsignal/power routes; firing and baking the plurality of stacked andpressed plurality of magnetic green sheets; singulating the plurality ofmagnetic green sheets to form a plurality of multilayer inductors; andplating external conductive patterns on the plurality of multilayerinductors.

In accordance with yet another aspect of the claimed invention, amultilayer inductor comprises a plurality of magnetic layers stacked oneupon the other; a spiral inductor element formed from electricallycoupled inductor conductive patterns formed on adjacent ones of theplurality of magnetic layers; and a plurality of electrically conductivesignal/power contacts formed on the edges of each of the plurality ofmagnetic layers, the plurality of electrically conductive signal/powercontacts forming external signal/power routes adapted to route signalsand power from a top magnetic layer to a bottom magnetic layer when theplurality of magnetic layers are stacked together.

In accordance with a further aspect of the claimed invention, method ofmanufacturing a multilayer inductor comprises the steps of providing aplurality of magnetic layers; forming internal vias on ones of theplurality of magnetic layers and forming external vias on each of theplurality of magnetic layers; forming conductive patterns on each of themagnetic layers, the conductive patterns including signal/power contactson the edges thereof and conductive external vias, the conductivepatterns formed on ones of the plurality of magnetic layers furthercomprising an inductor conductive pattern and a conductive internal via;and stacking the plurality of magnetic layers such that the inductorconductive patterns form a spiral inductor element and the signal/powercontacts form external signal/power routes.

There has been outlined, rather broadly, the more important features ofthe invention in order that the detailed description thereof thatfollows may be better understood, and in order that the presentcontribution to the art may be better appreciated. There are, of course,additional features of the invention that will be described below andwhich will form the subject matter of the claims appended herein.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of functional components andto the arrangements of these components set forth in the followingdescription or illustrated in the drawings. The invention is capable ofother embodiments and of being practiced and carried out in variousways. Also, it is to be understood that the phraseology and terminologyemployed herein, as well as the abstract, are for the purpose ofdescription and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be utilized as a basisfor the designing of other methods and systems for carrying out theseveral purposes of the present invention. It is important, therefore,that the claims be regarded as including such equivalent constructionsinsofar as they do not depart from the spirit and scope of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and features of the present invention willbecome apparent to those ordinarily skilled in the art upon review ofthe following description of specific embodiments of the invention inconjunction with the accompanying figures, wherein:

FIG. 1 is a schematic representation of a multilayer inductor in adisassembled configuration in accordance with a first embodiment of theinvention;

FIG. 2A is a top perspective view of the multilayer inductor of FIG. 1in the disassembled configuration;

FIG. 2B is a bottom perspective view of the multilayer inductor of FIG.1 in the disassembled configuration;

FIG. 3A is a top perspective view of the multilayer inductor of FIG. 1in a stacked configuration in accordance with the invention;

FIG. 3B is a bottom perspective view of the multilayer inductor of FIG.1 in the stacked configuration;

FIG. 4 is a top plan view of partial green sheet laminates in accordancewith the invention;

FIG. 5 is a top plan view of the partial green sheet laminates of FIG. 4showing saw lines in accordance with the invention;

FIG. 6 is a top plan view of the partial green sheet laminates of FIG. 5following singulation in accordance with the invention;

FIG. 7 is a flow chart of a multilayer inductor manufacturing process inaccordance with the invention;

FIG. 8 is a schematic representation of a multilayer inductor in adisassembled configuration in accordance with a second embodiment of theinvention;

FIG. 9 is a schematic representation of a multilayer inductor in adisassembled configuration in accordance with a third embodiment of theinvention;

FIG. 10 is a schematic representation of a multilayer inductor having aflip chip mounted on a top external conductive pattern thereof inaccordance with the invention; and FIG. 11 is a flow chart of asimplified multilayer inductor manufacturing process in accordance withthe invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The present invention will now be described in detail with reference tothe drawings, which are provided as illustrative examples of theinvention so as to enable those skilled in the art to practice theinvention. Notably, the figures and examples below are not meant tolimit the scope of the present invention. Where certain elements of thepresent invention can be partially or fully implemented using knowncomponents, only those portions of such known components that arenecessary for an understanding of the present invention will bedescribed, and detailed descriptions of other portions of such knowncomponents will be omitted so as not to obscure the invention. Further,the present invention encompasses present and future known equivalentsto the components referred to herein by way of illustration.

A first embodiment of a multilayer inductor in accordance with theinvention generally designated 100 is shown in FIG. 1. The multilayerinductor 100 includes a plurality n of magnetic layers laminatedtogether including a bottom magnetic layer 110 (corresponding to layer1), a top magnetic layer 170 (corresponding to layer n), andintermediate magnetic layers 150 (corresponding to layers 2 throughn-1). The bottom magnetic layer 110 includes a bottom externalconductive pattern 115 (shown in phantom lines and having a cross-hatchfill pattern) formed on a bottom surface 117 thereof. The bottomexternal conductive pattern 115 has a plurality of signal/power contacts120 formed at the edges thereof. Three such signal/power contacts 120are disposed on each of first and second adjacent sides of the bottommagnetic layer 110 in spaced relationship one to the other. Twosignal/power contacts 120 are disposed on each of third and fourthadjacent sides of the bottom magnetic layer 110 in spaced relationshipone to the other. The bottom external conductive pattern 115 alsoincludes a first inductor electrode 123 disposed internally of the edgesof the bottom magnetic layer 110 and a second inductor electrode 125,the second inductor electrode 125 having adjacent corner portions 127 aand 127 b disposed at a corner formed by the third and fourth sides ofthe bottom magnetic layer 110. The signal/power contacts 120 and thecorner portions 127 a and 127 b of the second inductor electrode 125have a semi-circular side profile as further described below and havesidewalls coated with a conductive material, e.g. metal, to provideelectrical connection therealong in a stacked configuration of themultilayer inductor 100.

The bottom magnetic layer 110 further includes an inductor conductivepattern 130 formed on a top surface 133 thereof. The inductor conductivepattern 130 has a first end 135 and tail end 137 and correspondsgenerally to seven eighths (⅞) of a turn of a spiral inductor element. Athrough hole 140 is formed in the bottom magnetic layer 110 and isdisposed at the first end 135 of the inductor conductive pattern 130. Atleast the sidewalls of the through hole 140 are coated with a conductivematerial, e.g., metal, which provides electrical connection between thefirst end 135 of the inductor conductive pattern 130 and the firstinductor electrode 123, a portion of which is disposed in underlyingrelationship to the first end 135. Such connection may be providedduring printing of the bottom external conductive pattern 115 andinductor conductive pattern 130.

The top magnetic layer 170 includes a top external conductive pattern175 formed on a top surface 177 thereof. The top external conductivepattern 175 includes a plurality of signal/power contacts 180 formed atthe edges thereof. Three signal/power contacts 180 are disposed on eachof first and second adjacent sides of the top magnetic layer 170 inspaced relationship one to the other. Two signal/power contacts 180 aredisposed on each of third and fourth sides of the top magnetic layer 170in spaced relationship one to the other. An inductor electrode contact185 includes adjacent corner portions 185a and 185b formed at a cornerformed by the third and fourth sides of the top magnetic layer 170. Onesof the signal/power contacts 180 further include internally disposedcontacts 183 electrically coupled to the signal/power contacts 180. Aninternally disposed contact 187 is electrically coupled to the inductorelectrode contact 185. The signal/power contacts 180 and the inductorelectrode contact corner portions 185 a and 185 b have a semi-circularside profile consistent with the side profiles of the signal/powercontacts 120 and the inductor electrode contact corner portions 127 aand 127 b of the second inductor electrode 125 as further describedbelow and have sidewalls coated with a conductive material, e.g. metal,to provide electrical connection therealong in the stacked configurationof the multilayer inductor 100.

Intermediate magnetic layers 150 each include a conductive pattern 151formed on a top surface 153 thereof. Each conductive pattern 151includes a plurality of signal/power contacts 160 and two adjacentinductor electrode contact corner portions 161 a and 161 b formed at acorner thereof. Three signal/power contacts 160 are disposed on each offirst and second adjacent sides of the intermediate magnetic layers 150in spaced relationship one to the other. Two signal/power contacts 160are disposed on each of third and fourth sides of the intermediatemagnetic layers 150 in spaced relationship one to the other. Inductorelectrode contact corner portions 161 a and 161 b are formed at a cornerformed by the third and fourth sides of the intermediate magnetic layers150. The signal/power contacts 160 and the inductor electrode contactcorner portions 161 a and 161 b have a semi-circular side profileconsistent with the side profiles of the signal/power contacts 120 and180 and the inductor electrode contact corner portions 127 a and 127 bof the second inductor electrode 125 and the inductor electrode contactcorner portions 185 a and 185 b as further described below. Thesignal/power contacts 160 and the inductor electrode contact cornerportions 161 a and 161 b have sidewalls coated with a conductivematerial, e.g. metal, to provide electrical connection therealong in thestacked configuration of the multilayer inductor 100.

Each conductive pattern 151 further includes an inductor conductivepattern 165 having a first end 167 and tail end 169. Each inductorconductive pattern 165 corresponds generally to seven eighths (⅞) of aturn of the spiral inductor element and is disposed upon eachintermediate magnetic layer 150 such that in a stacked configuration,the first end 167 thereof is vertically aligned with the tail end 169(137 in the case of bottom magnetic layer 110) of an underlying magneticlayer. A through hole 190 formed in each of the first ends 167 provideselectrical connection between the first end 167 and the tail end 169(tail end 137 in the case of the bottom magnetic layer 110) of anunderlying magnetic layer in the stacked configuration. The sidewalls ofthrough holes 190 are coated with a conductive material, e.g., metal, inorder to provide such electrical connection.

The intermediate magnetic layer 150 underlying the top magnetic layer170 (layer n-1) includes a trace 191 electrically connecting the tailend 169 of the inductor conductive pattern 165 to the inductor electrodecontact corner portions 161 a and 161 bInductor electrode contact cornerportions 161 a and 161 b are in turn electrically connected to theinductor electrode contact portions 185 a and 185 b formed on the topmagnetic layer 170 and to the second inductor electrode 125 on thebottom surface 117 of the bottom magnetic layer 110 as further describedbelow.

In accordance with the first embodiment of the invention, in order thatthe tail end 169 of inductor conductive pattern 165 of the intermediatemagnetic layer 150 underlying the top magnetic layer 170 (layer n-1) bedisposed in the position shown in FIG. 1, the number n must be 5+m8(where m=0, 1, 2. . . ). In the case where n=5the number of turns in thespiral inductor element is equal to 3.5In the case where n=13 the numberof turns in the spiral inductor element is equal to 10.5 and so on. Thenumber of magnetic layers (and thus the number of turns in the spiralinductor element) comprising the multilayer inductor 100 is determinedby multiple factors such as the inductance desired, the thickness ofeach magnetic layer, the overall thickness required and the flux densityof the multilayer inductor. One skilled in the art will recognize thatthe tail end 169 of the inductor conductive pattern 165 of theintermediate magnetic layer 150 underlying the top magnetic layer 170(layer n-1) may be disposed in a different position with appropriatemodification to the conductive patterns of the other magnetic layers soas to create a multilayer inductor having desired properties.Furthermore, the length and shape of the inductor conductive patterns130 and 165 and the shape and location of the first inductor electrode123 and the second inductor electrode 125, as well as the number ofturns and the number of magnetic layers may be modified to achievedesired properties. Selection of inductor conductive patterns 130 and165 having seven eighths (⅞) of a turn of the spiral inductor elementachieves more turns for a given number of magnetic layers but otherfractions are within the scope of the invention to meet variouscombinations of inductance and saturation requirements.

The bottom magnetic layer 110, the intermediate magnetic layers 150 andtop magnetic layer 170 are stacked one upon the other vertically asshown in FIGS. 2A and 2B. FIG. 2A is a perspective view showing the topsides of the bottom magnetic layer 110, the intermediate magnetic layers150, and the top magnetic layer 170 and FIG. 2B is a perspective viewshowing the bottom sides thereof. Three intermediate magnetic layers 150are shown. The intermediate magnetic layer 150 overlaying the bottommagnetic layer 110 is shown disposed such that the through hole 190formed at the first end 167 of the inductor conductive pattern 165thereof overlays the tail end 137 of the inductor conductive pattern 130of the bottom magnetic layer 110. Each successive intermediate magneticlayer 150 is similarly disposed such that the through hole 190 formed atthe first end 167 of the inductor conductive pattern 165 thereofoverlays the tail end 169 of the inductor conductive pattern 165 of theunderlying intermediate magnetic layer 150.

The intermediate magnetic layer 150 underlying the top magnetic layer170 is disposed such that the inductor electrode contact corner portions185 a and 185 b formed on the top magnetic layer 170 are disposeddirectly above the inductor electrode contact corner portions 161 a and161 b thereof. Each intermediate magnetic layer 150 is disposed suchthat the inductor electrode contact corner portions 161 a and 161 bthereof are disposed directly above the inductor electrode contactcorner portions 161 a and 161 b of the underlying magnetic layer. Theintermediate magnetic layer 150 overlaying the bottom magnetic layer 110is disposed such that the inductor electrode contact corner portions 161a and 161 b thereof are disposed directly above the inductor electrodecontact corner portions 127 a and 127 b of the second inductor electrode125. The inductor electrode contact corner portions 161 a and 161 b arebasically the same as the signal/power contacts 160, except thatinductor electrode contact corner portions 161 a and 161 b aredesignated for carrying the inductor current. In the stackedconfiguration, the signal/power contacts 120, 160 and 180 of the bottommagnetic layer 110, the intermediate magnetic layers 150 and the topmagnetic layer 170 respectively are aligned such that each signal/powercontact is disposed directly above an underlying signal/power contactand electrically coupled thereto to thereby provide vertical conductionof signals and power routed therealong. Exemplary power conductionincludes an input voltage (Vcc) to a power IC mounted on the topexternal conductive pattern 175 in a flip chip configuration.

In accordance with a process of the invention described below, followingthe formation of the through holes and conductive patterns on thebottom, top and intermediate magnetic layers, the magnetic layers arestacked and laminated together as shown in FIGS. 3A and 3B, to formsignal/power routes 300 from signal/power contacts 120, 160 and 180, andto form inductor power routes 350 from inductor electrode contact cornerportions 127 a,127 b,161 a,161 b,185 a,and 185 b.The top and bottomexternal conductive patterns 175 and 115, the signal/power routes 300and the inductor power routes 350 are plated following baking of themultilayer inductor 100. By way of example, the plating may benickel/tin plating. Such plating provides protection and strength to theexposed conductive areas and may further provide for additionalconductivity to signal/power routes 300 and inductor power routes 350.Signal/power routes 300 formed along side surfaces of the multilayerinductor 100 electrically connect the signal/power contacts 180 formedon the top magnetic layer 170, the signal/power contacts 160 formed onthe intermediate magnetic layers 150 and the signal/power contacts 120formed on the bottom magnetic layer 110. Inductor power routes 350formed along side surfaces of the multilayer inductor 100 electricallyconnect the inductor electrode contact corner portions 185 a and 185 bformed on the top magnetic layer 170, the inductor electrode contactcorner portions 161 a and 161 b formed on the intermediate magneticlayers 150, and the second inductor electrode corner portions 127 a and127 b formed on the bottom magnetic layer 110. In this manner, a chipmounted on the multilayer inductor 100 may be electrically connected tothe spiral inductor element at contact 187 with the inductor currentalso routed to the second electrode 125 by the inductor power routes350. In a preferred embodiment, the chip is a flip chip power integratedcircuit. In another preferred embodiment, the chip may be a regularpower integrated circuit that requires wire bonding interconnection.Signal and power inputs and outputs from the flip chip electricallyconnected to any of the contacts 183 on the top surface 177 of themultilayer inductor are routed to respective signal/power contacts 120on the bottom surface 117 of the multilayer inductor 100 by means ofrespective signal/power routes 300. Alternatively, a chip may beconnected to contacts 183 on the top surface 177 of the multilayerinductor through wire bonding. Thus a chip may be mounted on themultilayer inductor 100 and have electrical connections to a printedcircuit board (as shown in FIG. 10) along the sides of the multilayerinductor 100.

As will be appreciated by one skilled in the art, there is a great dealof flexibility in the design of the multilayer inductor 100 of theinvention. For example, the shape and size of the spiral inductorelement (the shape and size of each turn, the number of turns, thenumber of layers, etc.) may be adjusted according to design needs. Themagnetic layers may be of different shapes. The number of signal/powerroutes 300 and inductor power routes 350 may also be adjusted. In FIG.3A, only some of the signal/power routes 300 are used, but theallocation of the signal/power routes 300 may be easily adjusted bymodifying the top external conductive pattern 175. The location andnumber of inductor power routes 350 can also be easily modified. Ifrequired, a second inductor contact can be added to the top surface 177of the top magnetic layer 170. The inductor power routes 350 arebasically ones of the signal/power routes 300 designated and connectedto be used for carrying the inductor current.

The magnetic layers in accordance with the invention are preferablyformed from magnetic green sheets. Magnetic green sheets are made byapplying a slurry of magnetic ceramic material to a supporting film.After the magnetic ceramic material dries, the supporting film isstripped to yield the green sheet. The thickness of each green sheet canbe as thin as 50 microns such that a multilayer inductor formedtherefrom has a low profile. Each green sheet may contain a plurality ofunit layers that are used as a particular layer in a plurality ofmultilayer inductors. For example, a green sheet 400 (shown partially inFIG. 4) includes a plurality of rectangular unit magnetic layers 170(FIGS. 5 and 6) formed after singulation along saw lines 600 (FIG. 5).

A process 700 of manufacturing multilayer inductors in accordance withthe invention is shown in FIG. 7. FIGS. 4-6 are top views illustratingsome of the steps of the process 700 using top magnetic layers 170 as anexample. In a step 710 through holes or vias are formed at specificlocations of the green sheets 400. The specific locations are dependentupon the particular layer for which the green sheet will be employed.For example, through holes 410 are formed in the green sheet 400 toprovide the semi-circular side profile to the signal/power contacts 180and the inductor electrode contact corner portions 185 a and 185 b ofeach top magnetic layer 170 following singulation. Through holes 410 aredesignated external vias. Internal vias are also formed in the step 710.Exemplary internal vias include through holes 140 and 190 (FIG. 1).Through holes 410, 140 and 190 may be formed by conventional processesincluding drilling, punching, etching and laser cutting and preferablyhave a dimension between 30 and 500 microns. The shapes of the throughholes 410, 140 and 190 can also be other than circular including oval orrectangular shapes. Alternatively, the external vias may be formedfollowing the stacking step described below though the external vias soformed would be difficult to coat with conductive material at that stagesince the vias would be so deep.

Following the via formation step 710, in a step 720 conductive patterns151 are printed and cured on the green sheets comprising intermediatemagnetic layers 150, top external conductive patterns 175 are printedand cured on the green sheets comprising top magnetic layers 170, andbottom external conductive patterns 115 and the inductor conductivepattern 130 (if applicable) are printed and cured on the green sheetscomprising bottom magnetic layers 110. While printing the conductivepatterns 115, 175, 151 and 130, the sidewalls of the external vias 410and of the through holes 140 and 190 are also covered with theconductive paste. The conductive paste may include silver or otheroxidation-proof metal particles.

In a step 730, the green sheets are stacked in order one atop the otherand laminated and pressed to form the spiral inductor elements. Throughholes 190 provide electrical connection between inductor conductivepatterns 165 and the inductor conductive pattern 130 formed on thebottom magnetic layer 110 as previously described. Following the step730, in a step 740 the resulting laminate is fired and the conductivepaste forming the conductive patterns 151 and the inductor conductivepattern 130 is baked. The baking and firing may be performed together,or separately.

The top and bottom external conductive patterns 175 and 115, thesignal/power routes 300 and the inductor power routes 350 are nextplated with metal in a step 750. The laminated magnetic green sheets arethen singulated into individual multilayer inductors 100 in a step 760.After the singulation step 760, the halved external vias 410 provide theside profile of the contacts. Alternatively, the plating step 750 mayoccur after the singulation step 760 in order to better plate theexternal power/signal routes 300 and inductor power routes 350.Furthermore, the top and bottom conductive patterns may be printed afterthe stacking and pressing step 730. This may avoid potential damage tothe conductive patterns on the top and bottom surfaces during thestacking and pressing step 730. By way of example, the plating step 750may be performed using nickel (Ni) and/or Tin (Sn). The plating improvesthe durability of the exposed conductive patterns and reduces parasiticresistance.

As will be appreciated by one skilled in the art, there are manypossible variations to the method 700. The most essential steps informing the multilayer inductor of the invention are: a) forminginternal and external vias on magnetic material layers; b) formingconductive patterns on the magnetic layers to provide for the spiralinductor element; and c) stacking the magnetic layers to form the spiralinductor element and the external electrical routes. In the above steps,step b) may include forming inductor conductive patterns, signal/powercontacts, inductor power contacts, and external conductive patterns.

A second embodiment of a multilayer inductor in accordance with theinvention generally designated 800 is shown in FIG. 8. The multilayerinductor 800 includes a plurality n of magnetic layers laminatedtogether including a bottom magnetic layer 810 (corresponding to layer1), a top magnetic layer 870 (corresponding to layer n), andintermediate magnetic layers 850 (corresponding to layers 2 throughn-1). In contrast to the bottom magnetic layer 110 of the multilayerinductor 100, the bottom magnetic layer 810 does not have an inductorconductive pattern formed on a top surface 833 thereof. This maysimplify the manufacturing process since only one side of the bottommagnetic layer 810 needs to have a conductive pattern formed thereon.

The bottom magnetic layer 810 includes a bottom external conductivepattern 815 (shown in phantom lines and having a cross-hatch fillpattern) formed on a bottom surface 817 thereof. The bottom externalconductive pattern 815 has a plurality of signal/power contacts 820formed at the edges thereof. Three such signal/power contacts 820 aredisposed on each of first and second adjacent sides of the bottommagnetic layer 810 in spaced relationship one to the other. Twosignal/power contacts 820 are disposed on each of third and fourthadjacent sides of the bottom magnetic layer 810 in spaced relationshipone to the other. The bottom external conductive pattern 815 alsoincludes a first inductor electrode 823 disposed internally of the edgesof the bottom magnetic layer 810 and a second inductor electrode 825,the second inductor electrode 825 having adjacent corner portions 827 aand 827 b disposed at a corner formed by the third and fourth sides ofthe bottom magnetic layer 810. The signal/power contacts 820 and thecorner portions 827 a and 827 b of the second inductor electrode 825have a semi-circular side profile as described above with reference tosignal/power contacts 120 and the inductor electrode contact cornerportions 127 a and 127 b of the second inductor electrode 125 (FIG. 1).The sidewalls of the signal/power contacts 820 and the inductorelectrode contact corner portions 827 a and 827 b are coated withelectrically conductive material as in the first embodiment of theinvention.

A through hole 840 formed in the bottom magnetic layer 810 provideselectrical connection between the first inductor electrode 823 and aconductive pattern formed on the intermediate magnetic layer 850overlaying the bottom magnetic layer 810 as further described below. Thesidewall of the through hole 840 is coated with electrically conductivematerial as in the first embodiment of the invention.

The top magnetic layer 870 includes a top external conductive pattern875 formed on a top surface 877 thereof. The top external conductivepattern 875 includes a plurality of signal/power contacts 880 formed atthe edges thereof. Three signal/power contacts 880 are disposed on eachof first and second adjacent sides of the top magnetic layer 870 inspaced relationship one to the other. Two signal/power contacts 880 aredisposed on each of third and fourth sides of the top magnetic layer 870in spaced relationship one to the other. An inductor electrode contact885 includes adjacent corner portions 885 a and 885 b formed at a cornerof the third and fourth sides of the top magnetic layer 870. Ones of thesignal/power contacts 880 further include internally disposed contacts883 electrically coupled to the signal/power contacts 880. An internallydisposed contact 887 is electrically coupled to the inductor electrodecontact 885. The signal/power contacts 880 and the inductor electrodecontact corner portions 885 a and 885 b have a semi-circular sideprofile consistent with the side profiles of the signal/power contacts820 and the inductor electrode contact corner portions 827 a and 827 bof the second inductor electrode 825.

Intermediate magnetic layers 850 each include a conductive pattern 851formed on a top surface 853 thereof. Each conductive pattern 851includes a plurality of signal/power contacts 860 and two adjacentinductor electrode contact corner portions 861 a and 861 b formed at theedges thereof. Three signal/power contacts 860 are disposed on each offirst and second adjacent sides of the intermediate magnetic layers 850in spaced relationship one to the other. Two signal/power contacts 860are disposed on each of third and fourth sides of the intermediatemagnetic layers 850 in spaced relationship one to the other. Inductorelectrode contact corner portions 861 a and 861 b are formed at a cornerformed by the third and fourth sides of the intermediate magnetic layers850. The signal/power contacts 860 and the inductor electrode contactcorner portions 861 a and 861 b have a semi-circular side profileconsistent with the side profiles of the signal/power contacts 820 and880 and the corner portions 827 a and 827 b of the second inductorelectrode 825 and the inductor electrode contact corner portions 885 aand 885 b.

Each conductive pattern 851 further includes an inductor conductivepattern 865 having a first end 867 and tail end 869. Each inductorconductive pattern 865 corresponds generally to seven eighths (⅞) of aturn of the spiral inductor element and is disposed upon eachintermediate magnetic layer 850 such that in a stacked configuration,the first end 867 thereof is vertically aligned with the tail end 869 ofan underlying inductor conductive pattern 865. A through hole 890 formedin each of the first ends 867 provides electrical connection between thefirst ends 867 of each intermediate magnetic layer 850 and the tail ends869 of the underlying magnetic layer in the stacked configuration. Thethrough hole 890 of the intermediate magnetic layer 850 overlaying thebottom magnetic layer 810 provides electrical connection between firstend 867, the through hole 840 and first inductor electrode 823 of thebottom magnetic layer 810.

The intermediate magnetic layer 850 underlying the top magnetic layer870 (layer n-1) includes a trace 891 electrically connecting the tailend 869 of the inductor conductive pattern 865 to the inductor electrodecontact corner portions 861 a and 861 bInductor electrode contact cornerportions 861 a and 861 b are in turn electrically connected to theinductor electrode contact corner portions 885 a and 885 b formed on thetop magnetic layer 870 as previously described with reference to thefirst embodiment.

In accordance with the second embodiment of the invention, in order thatthe tail end 869 of the inductor conductive pattern 865 of theintermediate magnetic layer 850 underlying the top magnetic layer 870 bedisposed in the position shown in FIG. 8, the number n must be 6+m8(where m=0, 1, 2. . . ). In the case where n=6the number of turns in thespiral inductor element is equal to 3.5. In the case where n=14, thenumber of turns in the spiral inductor element is equal to 10.5 and soon. The number of magnetic layers (and thus the number of turns in thespiral inductor element) comprising the multilayer inductor 800 isdetermined by multiple factors such as the inductance desired, thethickness of each magnetic layer, the overall thickness required and theflux density of the multilayer inductor. One skilled in the art willrecognize that the tail end 869 of the inductor conductive pattern 865of the intermediate magnetic layer 850 underlying the top magnetic layer870 may be disposed in a different position with appropriatemodification to the conductive patterns of the other magnetic layers soas to create a multilayer inductor having desired properties.Furthermore, the length and shape of the inductor conductive patterns865 and the shape and location of the first inductor electrode 823 andthe second inductor electrode 825 may be modified to achieve desiredproperties. Selection of inductor conductive patterns 865 having seveneighths (⅞) of a turn of the spiral inductor element achieves more turnsfor a given number of magnetic layers but other fractions are within thescope of the invention to meet various combinations of inductance andsaturation requirements.

The bottom magnetic layer 810, the intermediate magnetic layers 850 andtop magnetic layer 870 are stacked one upon the other vertically asdescribed with reference to the first embodiment. The intermediatemagnetic layer 850 overlaying the bottom magnetic layer 810 is disposedsuch that the through hole 890 formed at the first end 867 of theinductor conductive pattern 865 thereof overlays the through hole 840formed through the first electrode 823. Each successive intermediatemagnetic layer 850 is disposed such that the through hole 890 formed atthe first end 867 of the inductor conductive pattern 865 thereofoverlays the tail end 869 of the inductor conductive pattern 865 of theunderlying intermediate magnetic layer 850.

The intermediate magnetic layer 850 underlying the top magnetic layer870 is disposed such that the inductor electrode contact corner portions885 a and 885 b formed on the top magnetic layer 870 are disposeddirectly above the inductor electrode contact corner portions 861 a and861 b thereof. Each successive intermediate magnetic layer 850 isdisposed such that the inductor electrode contact corner portions 861 aand 861 b thereof are disposed directly above the inductor electrodecontact corner portions 861 a and 861 b of the underlying magneticlayer. The intermediate magnetic layer 850 overlaying the bottommagnetic layer 810 is disposed such that the inductor electrode contactcorner portions 861 a and 861 b thereof are disposed directly above thecorner portions 827 a and 827 b of the second inductor electrode 825. Inthe stacked configuration, the signal/power contacts 820, 860 and 880 ofthe bottom magnetic layer 810, the intermediate magnetic layers 850 andthe top magnetic layer 870 are aligned such that each signal/powercontact is disposed directly above an underlying signal/power contact.

In accordance with a process of the invention described above, followingthe formation of the vias and conductive patterns on the intermediatemagnetic layers, the magnetic layers are stacked and laminated together.The top and bottom external conductive patterns 875 and 815 are thenplated. The resulting multilayer inductor 800 includes platedsignal/power routes (not shown) formed along side surfaces of themultilayer inductor 800 that include and electrically connect thesignal/power contacts 880 formed on the top magnetic layer 870, thesignal/power contacts 860 formed on the intermediate magnetic layers 850and the signal/power contacts 820 formed on the bottom magnetic layer810. Inductor power routes (not shown) formed along side surfaces of themultilayer inductor 800 electrically connect and include the inductorelectrode contact corner portions 885 a and 885 b formed on the topmagnetic layer 870, the inductor electrode contact corner portions 861 aand 861 b formed on the intermediate magnetic layers 850 and the secondelectrode contact corner portions 827 a and 827 b formed on the bottommagnetic layer 810. In this manner, a flip chip mounted on themultilayer inductor 800 may be electrically connected to the spiralinductor element at contact 887 with the inductor current routed to thesecond electrode 825 by the power routes. Signals and power from theflip chip electrically connected to any of the contacts 883 are routedto respective signal/power contacts 820 by means of respectivesignal/power routes.

In order to reduce flux density near the top and bottom of themultilayer inductor of the invention, a single magnetic layer ormagnetic layers not having inductor conductive patterns forming part ofthe spiral inductor element may be positioned adjacent to the top andbottom magnetic layers. These magnetic layers may also help to reduceinterference with electrical devices stacked above and/or below themultilayer inductor. With reference to FIG. 9, a third embodiment of theinvention includes a multilayer inductor 900 having a plurality ofmagnetic layers laminated together including a bottom magnetic layer910, a top magnetic layer 980, intermediate magnetic layers 950 and fluxdensity reducing magnetic layers 960-1 and 960-2. The bottom magneticlayer 910, the top magnetic layer 980 and the intermediate magneticlayers 950 are in all respects identical to the bottom magnetic layer810, the top magnetic layer 870 and the intermediate magnetic layers 850respectively of the second embodiment of the invention.

The flux reducing magnetic layer 960-1 is disposed in overlayingrelationship to the bottom magnetic layer 910 and includes a conductivepattern 961 formed on a top surface 963 thereof. The conductive pattern961 includes signal/power contacts and inductor electrode contactportions disposed at the edges thereof to provide signal/power routingand inductor power routing as described with reference to the first andsecond embodiments of the invention. A through hole 965 formed in theflux reducing magnetic layer 960-1 provides electrical connectionbetween an inductor conductive pattern 965 formed on an intermediatemagnetic layer 950 disposed in overlaying relationship to the fluxreducing magnetic layer 960 and a first electrode 923 of the bottommagnetic layer 910.

The flux reducing magnetic layers 960-2 (two are shown) are disposed inunderlying relationship to the top magnetic layer 980 and includeconductive patterns 970 formed on top surfaces 971 thereof. Theconductive patterns 970 include signal/power contacts and inductorelectrode contact portions disposed at the edges thereof to providesignal/power routing and inductor power routing as described withreference to the first and second embodiments of the invention. Oneskilled in the art will recognize that the third embodiment can bemodified to include more or less flux reducing magnetic layers 960-1 and960-2 to thereby provide for different flux densities near the top andbottom of the multilayer inductor of the invention.

With reference to FIG. 10, a flip chip 1000 is shown disposed on the topexternal conductive pattern 175 of the multilayer inductor 100.Electrical connection between contacts of the flip chip 1000 andcontacts 183 and 187 of the top external conductive pattern 175 are madeby means of solder balls 1010. Signal/power routes 300 and power routes350 provide signal/power and inductor power routing to signal/powercontacts 120 and corner portion 127 a of the second electrode 125 thatare in turn connected to contacts (not shown) of a printed circuit board(PCB) 1020. The first and second inductor electrodes 123 and 125 mayalso be connected to contacts (not shown) of the printed circuit board1020. By way of example, solder paste 1021 may be used to attach themultilayer inductor 100 to the PCB 1020. In a preferred embodiment, theflip chip 1000 may be a power control chip.

FIG. 11 shows a simplified method 1100 for manufacturing a multilayerinductor of the invention. After a step 1110 of providing magneticlayers, in a step 1120, internal vias are formed on ones of the magneticlayers and external vias are formed on each of the magnetic layers. In astep 1130, conductive patterns are formed on each of the magneticlayers. The conductive patterns may include inductor conductivepatterns, signal/power contacts, and patterns on the internal andexternal vias. In a step 1140, the magnetic layers are stacked such thatthe inductor conductive patterns form a spiral inductor element and thesignal/power contacts form external signal/power routes. The top of themultilayer inductor may be adapted to receive a semiconductor chip suchas an integrated circuit (IC) chip, a flip chip, or a power controlchip. The bottom of the multilayer inductor may be adapted for mountingon a circuit board. Forming the signal/power contacts may furthercomprise forming external vias on each of the magnetic layers, forming aconductive pattern on the external vias, and singulating the magneticlayers through the external vias. There may be an additional step ofsingulating the inductors through the external vias.

The multilayer inductor of the invention provides a cost-effectivestructure having a relatively small thickness and a compact size thataccommodates a semiconductor chip in a flip chip configuration on a topexternal conductive pattern thereof. Signal/power and inductor powerrouting is achieved by means of conductive patterns formed on sidesurfaces of the multilayer inductor that route signals/power andinductor power from the top external conductive pattern to a bottomexternal conductive pattern. The process of manufacturing the multilayerinductor provides for the formation of the signal/power and inductorpower routing conductive patterns concurrently with the formation ofinductor conductive patterns to thereby reduce the number ofmanufacturing steps. In a preferred embodiment, the multilayer inductorof the invention is a power inductor suitable for use with powersemiconductors such as power MOSFETs, and power control chips. Althoughthe invention describes the spiral inductor element of the multilayerinductor in great detail, the signal/power and inductor power routingmay be applied to any multilayer inductor. Conductive side contacts areformed on each layer of the multilayer inductor such that they formsignal/power and inductor power routes when the layers are stackedtogether.

It is apparent that the above embodiments may be altered in many wayswithout departing from the scope of the invention. Further, variousaspects of a particular embodiment may contain patentably subject matterwithout regard to other aspects of the same embodiment. Still further,various aspects of different embodiments can be combined together.Accordingly, the scope of the invention should be determined by thefollowing claims and their legal equivalents.

1. A multilayer inductor comprising: a bottom magnetic layer includingan external conductive pattern formed on a bottom surface thereof, theexternal conductive pattern including a plurality of signal/powercontacts disposed at edges thereof and first and second inductorelectrodes; a top magnetic layer including an external conductivepattern formed on a top surface thereof, the external conductive patternincluding a plurality of signal/power contacts disposed at edges thereofand an inductor electrode contact; and a plurality of intermediatemagnetic layers stacked between the bottom magnetic layer and the topmagnetic layer, each intermediate magnetic layer including a pluralityof signal/power contacts disposed at edges thereof and an inductorconductive pattern, each of the plurality of intermediate magnetic layersignal/power contacts electrically coupled to respective top and bottommagnetic layer signal/power contacts to form external signal/powerroutes between the top magnetic layer external conductive pattern andthe bottom magnetic layer external conductive pattern, each of theintermediate magnetic layer inductor conductive patterns coupled to eachother to form a spiral inductor element, the spiral inductor elementcoupled at a first end thereof to the top magnetic layer inductorelectrode contact and at a second end thereof to the first inductorelectrode, the top magnetic layer inductor electrode contact coupled tothe second inductor electrode by an external inductor power route,comprising at least one of the external signal/power routes.
 2. Themultilayer inductor of claim 1, wherein the bottom magnetic layerfurther comprises an inductor conductive pattern formed on a top surfacethereof, the bottom magnetic layer inductor conductive pattern beingcoupled to an intermediate magnetic layer inductor conductive pattern ofan overlaying intermediate magnetic layer to form part of the spiralinductor element.
 3. The multilayer inductor of claim 2, wherein thebottom magnetic layer inductor conductive pattern includes a first endand a tail end, the first end being electrically coupled to the firstinductor electrode by means of a through hole formed through the firstend.
 4. The multilayer inductor of claim 1, wherein the top magneticlayer external conductive pattern is adapted to receive a semiconductorchip.
 5. The multilayer inductor of claim 4, wherein the semiconductorchip comprises an integrated circuit chip.
 6. The multilayer inductor ofclaim 4, wherein the semiconductor chip is a flip chip integratedcircuit.
 7. The multilayer inductor of claim 1, wherein the bottommagnetic layer external conductive pattern, the top magnetic layerexternal conductive pattern, and the signal/power contacts and theinductor conductive patterns of the intermediate magnetic layerscomprise a conductive paste.
 8. The multilayer inductor of claim 7,wherein the conductive paste includes silver particles.
 9. Themultilayer inductor of claim 1, wherein the bottom magnetic layerexternal conductive pattern, the top magnetic layer external conductivepattern, and the signal/power routes are plated.
 10. The multilayerinductor of claim 1, wherein the bottom magnetic layer first inductorelectrode is disposed internally of the edges of the bottom magneticlayer and the second inductor electrode includes adjacent portionsdisposed at the edges of adjacent sides of the bottom magnetic layer.11. The multilayer inductor of claim 1, wherein each intermediatemagnetic layer inductor conductive pattern includes a first end and atail end, the first ends of inductor conductive patterns of overlayingintermediate magnetic layers being electrically coupled to the tail endsof inductor conductive patterns of underlying intermediate magneticlayers by means of through holes formed through the first ends.
 12. Themultilayer inductor of claim 1, further comprising a plurality of bottomflux density reducing magnetic layers, the plurality of bottom fluxreducing magnetic layers being disposed in overlaying relationship tothe bottom magnetic layer and having a conductive pattern formed on asurface thereof, each conductive pattern including signal/power contactsdisposed at edges thereof, and a through hole providing electricalconnection between the inductor conductive pattern formed on theintermediate magnetic layer overlaying the plurality of bottom fluxreducing magnetic layers and the first electrode of the bottom magneticlayer.
 13. The multilayer inductor of claim 1, further comprising aplurality of top flux density reducing magnetic layers, the plurality oftop flux reducing magnetic layers being disposed in underlyingrelationship to the top magnetic layer and having a conductive patternformed on a surface thereof, each conductive pattern includingsignal/power contacts disposed at edges thereof.
 14. The multilayerinductor of claim 1, wherein the external conductive pattern on thebottom magnetic layer is adapted to be mounted on a printed circuitboard.
 15. The multi-layer inductor of claim 1, wherein the multi-layerinductor accommodates a semiconductor chip in a flip chip configuration,and wherein each layer contains ⅞ turns of conductive trace on onesurface except for the top layer.